1. Field of Invention
The invention relates to a passive alignment packaging structure and, in particular, to a passive alignment packaging structure for opto-electrical devices and optic fiber connectors.
2. Related Art
With the rapid development of the Internet and to follow the future trend in high-speed broadband communications, there is a higher demand in communication speed and quality. Optical communications using optic fiber networks has become the emphasis in the communication industry. Optic fiber products related to optical communications also become more important. The optical transceiver that emits and receives optical signals is a significant device in optical active devices. High-speed transmission systems using optic fibers as the media require high-quality optical transceivers for support.
As electronics packaging becomes more compact and the optical transmission speed keeps increasing, the packaging of the optical transceiver also becomes smaller. Under the high precision requirement of the coupling efficiency between the laser source and the optic fiber, the alignment is of greater importance. Moreover, the newly developed optical communication device technology utilizes surface-emitting and surface-detecting devices. Such devices include the vertical cavity surface emitting laser (VCSEL) and the PIN photodiode. These make the optical path alignment of the optical transceiver even harder.
Currently, the commonly adopted active alignment is performed manually. It takes a longer time and requires a large amount of manpower. Therefore, this method is not ideal for mass production. In contrast, the passive alignment packaging is more suitable for automatic production at a lower cost. The known passive alignment includes the following methods. In the design of the U.S. Pat. No. 5,905,831, a V-shape groove is formed on a substrate and an opto-electrical device by etching for installing an optic fiber. A square groove is made on the vertical direction of the substrate to accommodate the device. This method allows a passive alignment between the device and the optic fiber. However, the precision of the alignment in this method is determined by the error and precision due to machining. In the U.S. Pat. No. 5,499,312, the chip mounting technology is used to perform passive alignment between the optical waveguide and the opto-electrical device. The optical waveguide, the base, and the opto-electrical device are connected by soldering. The surface tension of the solder ball produces the self-alignment effect. This method is used in edge-emitting laser opto-electrical devices. The alignment requires precision calculation of the solder ball distribution and the granular size in order to achieve the optimized alignment effect.
Moreover, in the U.S. Pat. No. 5,499,312, a guiding pin is used to directly penetrate through the substrate and the lens to form an aligned structure with the optic fiber connector. However, directly making through holes on the substrate and the lens is likely form localized stress. The thermal expansion caused by temperature change can damage the substrate and lens. The yield and reliability are hard to increase.
In view of the foregoing, an objective of the invention is then to provide a passive alignment packaging for opto-electrical devices and optic fiber connectors. A precision passive alignment packaging structure is employed to satisfy the requirements for a precision optical path. Furthermore, the passive alignment packaging is beneficial for automatic assembly for lowering the manufacturing cost.
Another objective of the invention is to design a precision passive alignment packaging structure from an opto-electrical device to an optic Fiber connector. According to the disclosed technique, the passive alignment packaging structure contains: a base, a leadframe, and a micro lens set. The base surface has two guiding pins. The leadframe is connected to a silicon substrate by soldering. The silicon substrate is further installed with an opto-electrical device. The micro lens set contains a lens support and a set of lenses to focus light. The two guiding pins on the base align and connect the leadframe and the lens support. The leadframe and the lens support have two through holes corresponding to the number and positions of the guiding pins. The guiding pins penetrate through the leadframe and the lens support, directly having the vertical alignment. The soldering between the silicon substrate and the leadframe performs the horizontal alignment. Therefore, the optical path from the opto-electrical device to the optic fiber connector can be precisely aligned.
In addition, the two through holes on the leadframe and the lens support have alignment and stress relaxation designs to reduce deformation caused by guiding pin insertion during the assembly. Errors produced during the through hole manufacturing process can be reduced. The invention also avoids damages on the guiding pins and device caused by localized stress due to thermal expansion. The yield and reliability can be effectively increased.